JPCERT-AT-2026-0035
JPCERT/CC
2026-11-11

I. Overview

Microsoft has released November 2026 Security Updates to address the vulnerabilities in their products. Attackers leveraging these vulnerabilities may be able to execute arbitrary code remotely or obtain sensitive information, etc.

Microsoft Corporation
November 2026 Security Updates
https://msrc.microsoft.com/update-guide/releaseNote/2026-Nov

According to Microsoft, among the vulnerabilities, the following vulnerability has been confirmed to be exploited in the wild. If exploited, this vulnerability could cause Outlook to connect to an attacker-controlled server without displaying the usual security warning when a user opens a specially crafted message file, potentially resulting in the disclosure of authentication credentials. Please refer to the latest information provided by Microsoft and implement the measures described in "II. Solution."

CVE-2026-124194
Microsoft Outlook Spoofing Vulnerability
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-124194
Note: This vulnerability is classified as CWE-356: Product UI does not Warn User of Unsafe Actions

II. Solution

Please apply the security update programs through Microsoft Update, Windows Update, etc.

Microsoft Update Catalog
https://www.catalog.update.microsoft.com/

Windows Update: FAQ
https://support.microsoft.com/en-us/help/12373/windows-update-faq

III. References

Microsoft Corporation
Release Notes
https://msrc.microsoft.com/update-guide/


If you have any information regarding this alert, please contact JPCERT/CC.

JPCERT Coordination Center (Cyber Security Coordination Group)
MAIL: ew-info@jpcert.or.jp
https://www.jpcert.or.jp/english/